Characterization of Bacillus cereus Group Isolates From Human Bacteremia by Whole-Genome Sequencing

Abstract

Members of the Bacillus cereus group are spore-forming organisms commonly associated with food poisoning and intestinal infections. Moreover, some strains of the group (i.e., B. cereus sensu stricto and Bacillus thuringiensis) can cause bacteremia in humans, mainly in immunocompromised individuals. Here we performed the genetic characterization of 17 human clinical strains belonging to B. cereus group isolated from blood culture. The whole-genome sequencing (WGS) revealed that the isolates were closely related to B. cereus sensu stricto and B. thuringiensis–type strain. Multilocus sequence typing analysis performed on the draft genome revealed the genetic diversity of our isolates, which were assigned to different sequence types. Based on panC nucleotide sequence, the isolates were grouped in the phylogenetic groups III and IV. The NHE, cer, and inhA gene cluster, entA, entFM, plcA, and plcB, were the most commonly detected virulence genes. Although we did not assess the ability to generate biofilm by phenotypic tests, we verified the prevalence of biofilm associated genes using an in silico approach. A high prevalence of pur gene cluster, xerC, clpY, codY, tasA, sipW, sinI, and sigB genes, was found. Genes related to the resistance to penicillin, trimethoprim, and ceftriaxone were identified in most of the isolates. Intriguingly, the majority of these virulence and AMR genes appeared to be evenly distributed among B. cereus s.s. isolates, as well as closely related to B. thuringiensis isolates. We showed the WGS represents a good approach to rapidly characterize B. cereus group strains, being able to give useful information about genetic epidemiology, the presence of virulence and antimicrobial genes, and finally about the potential hazard related to this underestimated risk.

Comparative analysis of Bacillus cereus group isolates’ resistance using disk diffusion and broth microdilution and the correlation between resistance phenotypes and genotypes

“…One study performed by Bianco et al investigated the prevalence of AMRg in a collection of 17 B. cereus group, clinical blood isolates (46). Similar to our collection, there was a high prevalence of beta-lactamases in the Bianco et al collection, specifically Bla-1 and Bla-2 (46). Our collection had a much higher percentage of the blaZ beta-lactam compared to the prevalence of this gene in the 17 clinical isolates (46).…”

Genomic Surveillance of Circulating SARS-CoV-2 in South East Italy: A One-Year Retrospective Genetic Study

“…Amplicons from both primer pools were combined and purified with a 1× volume of Ampure XP beads (Beckman Coulter, CA, USA). Approximately 300 ng of each purified sample of multiplexed PCR amplicons obtained was used for library preparation with Nextera DNA Flex sample preparation kit (Illumina), according to the manufacturer’s instructions [ 15 ]. Sequencing was performed on the Illumina MiSeq platform (Illumina) using the MiSeq Reagent Kit v2, 2 × 250 paired-end cycles.…”

Antimicrobial Effects of Potential Probiotics of Bacillus spp. Isolated from Human Microbiota: In Vitro and In Silico Methods

“…The strains isolated in the present work were clustered in the two main groups: B. subtilis –like (non-pathogenic) [ 59 ] and B. cereus -like (pathogenic) [ 60 ], as shown in Figure 3 , however the pathogenicity features are strain-specific dependent. The work approach is based on potential uses and predictive data analysis, but for further commercial uses, a safety assessment should be performed for each strain, to demonstrate that they do not pose any safety and/or pathogenicity concerns.…”